Friday, 18 July 2014

What you are looking at is tiles stored in a MBTiles database. The Android app in question is Locus Map, which supports MBTiles databases. MBTiles is an ideal format for delivering tiled maps to mobile devices. It's just a SQLite database that uses the same intuitive XYZ tiling scheme used by OpenStreetMap and friends.

This post will show you how to make such MBTiles databases with a little help from the mapguide-rest extension.

[NOTE: These instructions were used against the current master branch of mapguide-rest which supercedes the 0.8 release, and has several fixes for tile caching. These instructions may or may not work on the 0.8 release]

Note the {$x}, {$y} and {$z} placeholder tokens in the URL. These placeholders are required and Portable Basemap Server will be replacing them with actual X, Y and Z values when fetching tiles.

Once you've edited and saved CustomOnlineMaps.xml, run the PortableBasemapServer.exe as an administrator.

What is unique about Portable Basemap Server (and something I could not find in any other free/OSS packages), is that Portable Basemap Server includes a convenient function to create an MBTiles database from any online tiled map (that presumably follows a XYZ tiling scheme). This function is accessible from the Format Convert menu.

In the Format Convert window, change the Data Source Type to the map source you registered in CustomOnlineMaps.xml. If your tiled map does not span the entire world, you may want to hone in to the specific region your tiled map is in with one of the existing map sources before switching over to your mapguide-rest map source.

Now do the following:

Specify the path of the MBTiles database you want to create

Trace a box around the area you want to fetch the tiles for

Tick the Download Levels (aka. Zoom levels) you want to fetch tiles for. The map preview shows the current zoom level, so generally you want to tick that level and every level above that.

Tick Compact? to optimize storage of redundant tiles

Once you are satisfied with the settings, click Start to initiate the tile seeding process. Portable Basemap Server will spit out lots of useful progress information while building the MBTiles database.

Once the tile seeding process is complete, you can now transfer this MBTiles database file to your mobile device and load it into your MBTiles supported app.

As a bonus, the actual process of building an MBTiles database also seeds the XYZ tile cache on the server-side. So this process can also serve as a XYZ tile cache seeder if you have no use for MBTiles.

If you're interested in what platforms support MBTiles, check out the MBTiles wiki.